Abstract The goal of this research is to establish an intraoperative tool for measuring ligament tension during total knee arthroplasty (TKA). This technology would enable surgeons to identify and correct individual structures that may be improperly tensioned, which could mitigate post-operative pain, stiffness, and instability. We have recently shown that the speed at which shear waves propagate in tendons and ligaments can be measured and used to infer the tension in the structure. In this project, we will construct and test a handheld device suitable for intraoperative measurements of shear wave speed in ligaments. The device, termed a shear wave tensiometer, will induce and track propagating shear waves of micron- scale amplitude. In Aim 1, we will measure shear wave speeds in isolated superficial medial and lateral collateral ligaments (sMCL and LCL) and patellar ligaments (PL) undergoing axial loading. These experiments will be used to investigate the effects of ligament cross-sectional geometry on the shear wave speed-tension relationship. In Aim 2, we will measure shear wave speeds in the sMCL and LCL following incremental ligament releases, which are performed intraoperatively to reduce the tension in an overly-tight ligament. These experiments will be used to assess the sensitivity with which ligament shear wave speed data can be used to objectively guide incremental releases. In Aim 3, TKA will be performed on cadaveric knees. Three-dimensionally printed femoral, tibial, and patellar components will be used to simulate subtle adjustments in component alignment that would represent those made clinically. We will perform standard clinical assessments of knee laxity and range-of-motion while ligament shear wave speeds, externally applied loads, and joint kinematics are simultaneously measured. These experiments will be used to assess the sensitivity with which ligament shear wave speed data can be used to guide subtle adjustments in component alignment. The outcome of this study will be a novel intraoperative approach needed by surgeons to objectively plan, execute, and evaluate TKAs, which should improve patient satisfaction and reduce the need for revision procedures. Beyond TKA, the fundamental technology has broader relevance for objectively assessing ligament behavior following injury, during healing, and due to diseases such as osteoarthritis.